introduced MutableWorkspaceState#store(OutputStream)

... this is needed to suppress unnecessary output files writes
during incremental build.

Signed-off-by: Igor Fedorenko <igor@ifedorenko.com>
diff --git a/src/main/java/org/eclipse/m2e/workspace/MutableWorkspaceState.java b/src/main/java/org/eclipse/m2e/workspace/MutableWorkspaceState.java
index ca60805..5439b8d 100644
--- a/src/main/java/org/eclipse/m2e/workspace/MutableWorkspaceState.java
+++ b/src/main/java/org/eclipse/m2e/workspace/MutableWorkspaceState.java
@@ -50,7 +50,14 @@
       throw new IOException("Could not create directory " + dir);
     }
     try (OutputStream os = new BufferedOutputStream(new FileOutputStream(file))) {
-      state.store(os, null);
+      store(os);
     }
   }
+
+  /**
+   * @since 0.2
+   */
+  public void store(OutputStream os) throws IOException {
+    state.store(os, null);
+  }
 }